Electromagnetic latching device



QC 24, 96 TAKEO SHINOHARA 3,349,356

ELECTROMAGNETIC LATCHING DEVICE Filed Nov. 1.7, 1965 ICE.

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1 N VEN TOR 7' 1%? 0 .5////V 4 1917/6? 4377 157 44; 595.50; Ghee 53pm United States Patent 3,349,356 ELECTROMAGNETIC LATCHING DEVICE Takeo Shinohara, Tokyo, Japan, assignor to Nippon Electric Company Limited, Tokyo, Japan Filed Nov. 17, 1965, Ser. No. 508,237 Claims priority, application Japan, Nov. 20, 1964, 39/ 65,488 7 Claims. (Cl. 335-254) The instant invention rel-ates to electromagnets and more particularly to an electromagnet assembly for use as a control device which may :be operated through the intermittent use of a signal and yet be capable of maintaining either the operated or released state in the absence of a signal and without the consumption of electric power.

Conventional electromagnets presently in use are quite frequently employed as magnetic latching relay devices since they fit all of the functional requirement-s for such applications. However, conventional electromagnets have certain dis-advantages. Since the operating margin is quite limited, these devices may erroneously reoperate if a large current is erroneously passed therethrough at the time of release. Moreover, it is necessary in order to perform the operating and releasing functions to provide two coils for the changeover operation or to pass currents of reverse magnitudes through a single coil, either of which approach complicates the circuit design for the device.

The instant invention is characterized by providing an electromagnet control device which has an unlimited operating margin, permits straightforward selective operation for closure or release and is extremely reliable and stable.

The instant invention is comprised of a core of ferromagnetic material, preferably of semi-hard consistency, having an elongated configuration. The armature member is preferably pivotally mounted at one end and has the opposite end thereof positioned in close proximity tothe core member intermediate the ends thereof. Biasing means are provided for normally urging the free end of the armature member away from the core member. The first one of said coils is wound a predetermined number of times about a first end of the core and is wound with half as many turns near the second end of the core. The second of the pair of coils is wound a predetermined number of times about the second end of said core and is Wound half as many times around the first end of the core so that the lesser number of windings of said'second coil is in close proximity to the greater number of Windings of said first coil and vice-versa, at the opposite ends of the core. No windings are provided in the intermediate region of said core.

When a current of a predetermined magnitude and direction is passed through either one of said coils to the exclusion of the other a magnetic flux pattern is set up such that the magnetic flux lines which are parallel to the longitudinal axis of the core is of substantially constant strength over almost the entire length of the core. The magnetic flux which is normal to the longitudinal axis of the core is of zero strength at the intermediate portion of the core and is of substantial strength at the opposite ends of the core. Since the strength of the normal magnetic flux is zero at the intermediate ortion of the core member no attractive force is imposed upon the armature member in close proximity thereto. If currents of substantially the same magnitude and direction are passed through both pairs of coils a magnetic flux pattern is set up in which the field substantially parallel to the longitudinal axis of the core is of zero field strength inthe intermediate region ofthe core and in which the 3,349,356 Patented Oct. 24, 1967 flux pattern normal to the longitudinal axis of the coil is of maximum field strength in the intermediate region of the core. The presence of a field of maximum strength in the normal direction to the longitudinal axis of the core exerts an attractive force upon the armature member so as to urge the armature member toward the core member against the mechanical biasing force exerted thereon. Removal of the currents from the pair of coils does not remove the magnetic flux pattern from the core due to its retentivity characteristics, thereby maintaining the armature member into engagement with its associated core member. The magnetic flux pattern normal to the longitudinal axis of the core and in the intermediate region of the core can be removed only through the application of signals of the same magnitude, but of reverse direction from those signals which have been applied to the coils to set u the normal flux pattern in the intermediate region of the core. Even after removal of the reverse current signals the core will be maintained in the quiescent state allowing the armature member to return to its normal position out of engagement with the core member under control of the mechanical biasing means. Successful latching or releasing operations can be obtained even though the current magnitudes of the latching or releasing currents are not exactly equal to one another and the actual magnitudes of the currents are not critical so long as the magnitudes are at least sufficient to set up a flux pattern normal to the longitudinal direction of the core in the intermediate region of the core which is of sufiicient strength to overcome the mechanical biasing force exerted upon the armature member. The arrangement of the instant invention thus provides an extremely simple electromagnet control device which is reliable, easy to operate, has an unlimited operating margin and is capable. of remaining in either the latched or released statein the absence of electrical power.

It is therefore one object of the instant invention to provide a novel electromagnet control device.

Another object of the instant invention is to provide a novel electromagnet control device employing a ferrosteel, or V-Fe-Co alloy (having a trade name of 2V' magnetic core member.

Still another object of the instant invention is to provide a novel electromagnet control device comprised of a ferromagnetic core member and pairs of windings applied at opposite ends of the core member for setting up a magnetic flux pattern normal to the longitudinal axis of the core for latching the armature device.

Still another object of the instant invention is to provide a novel electromagnet control device comprised of a ferromagnetic core member and pairs of windings applied at opposite ends of the core member for setting up a magnetic flux pattern normal to the longitudinal axis of the core for latching the armature device wherein the device is capable of remaining in either the latched or released state in the absence of any electrical power.

These and other objects of the instant invention Will become apparent when reading the accompanying description and drawings in which:

FIGURE 1 is a perspective view showing an electromagnet control device designed in accordance with the principles of the instant invention.

FIGURES 2(a)2(c) are plots showing the relations between the magnetomotive forces applied to the control device of FIGURE 1 and the magnetic flux pattern set up as a result of the applied magnetomotive forces.

Referring now to the drawings, FIGURE 1 shows an electromagnet control device 10 comprised of an elongated core member 11 preferably formed of a semi-hard ferromagnetic material such as carbon steel, tungsten Permender or 4V Permender). An armature member 14 forming part of the device has a first end thereof secured to a shaft or rod 14a which is journalled to pivot within stationary mounted supports 14b and 140, respectively, so as to permit rotation of armature 14 in either of the two opposing directions denoted by arrows 17 and 18, respectively. The armature 14 is preferably comprised of a soft ferromagnetic material such as elec-v tromagnetically pure iron, silicon steel, or Fe-Ni alloy (having a trade name of Permalloy).

In the released state, which state is to be more fully described, the armature 14 is maintained a spaced distance away from the intermediate portion of core 11 by means of a biasing spring 15 having a first end attached to a stationary support and a second end thereof secured to the free end of armature 14. The air gap 16 between core 11 and armature 14 is maintained at a constant distance by means of the stop member 19, armature 14 being cause-d to bear against stop member 19 under the biasing force of spring 15 The control device is provided with a pair of coils 12-12 and 13-13 whose windings are divided into two sections with the dividing area being the intermediate region of core 11. The first of the two coils, namely the coil 12-12 has a first number of windings 12 near the upper end of core 11 and a second number of windings 12 near the lower end of core 11 with the number of windings 12 being substantially equal to one-half the number of windings 12. With regard to the remaining coil 13-13 the number of windings 13 are equal to substantially half the number of the windings 13. The windings 12 and 12 are wound clockwise about core 11 relative to their input terminal a. The windings 13' and 13 are wound counterclockwise about core 11 relative to their input terminal c. The windings 1 2-12 and 1313 are connected in series by the conductors 12a and 13a, respectively, so as to set up cooperating magnetic fields within core 11 upon the receipt of magnetizing current. FIGURE 2 shows the resulting magnetomotive forces and flux patterns set up within ferromagnetic core 11 upon the application of current signals. 1

As a first example, let it be assumed that a current signal I is applied to the terminals a-b of windings 12 and 12. If the number of turns of the windings 12 and 13 is 2N and the number of turns of the windings 12' and 13 is N, then the current I, having the direction shown, is applied to the terminals ab. The resulting magnetomotive forces generated by the windings 12 and 12' within core 11 are shown by the arrows 21 and 21. Solid line curve 71, in FIGURE 2(a) represents the strength of the magnetic flux along the length of core 11 which is substantially parallel to the longitudinal axis 11 of core 11 (see FIGURE 1). The magnetic flux generated by the magnetomotive forces 21 and 21' which is normal to the longitudinal axis 11' is shown by the dotted line curve 81. It "can be seen that the field strength of the magnetic flux normal to the longitudinal axis of the core is of zero field strength at the center of the core and is of maximum field strength at the ends. of the core.

Let it now be assumed that the current signal I of the direction as shown in FIGURE 1, is now applied to the terminals c and d of windings 13-13.. As shown in FIGURE 2(b) the magnetomotive forces are represented by the arrows 31 and 31'. Their directions are opposite to the magnetomotive forces 21' and 21 due to the reverse direction of the windings 13' and 13. The resulting mag netic fluxes which are generated are shown by the curves of FIGURE 2(b) wherein the magnetic flux which is parallel to the core longitudinal axis 11 is represented by the solid line curve 72. It can be seen that the strength of the parallel magnetic flux pattern is substantially constant along theentire length of core 11. The magnetic flux which is normal to the longitudinal axis 11" of core ll is represented by the dotted line curve 82. It can clearly be seen that the normal flux pattern has zero field strength magnetomotive forces at the upper end of core 11 will be equal to 2NlNI=NI. The resultant magnetomotive force is shown in FIGURE 2(c) by the arrow 23.

Considering the windings 12 and 13, the resultant magnetomotive force is Nl.2 NI= NI This resultant magnetomotive force is shown in FIGURE 2(c) by the arrow 32. The resultant magnetomotive forces 23 and 32 set up magnetic flux patterns such that the magnetic flux pattern which is substantially parallel to the core longitudinal axis 11 is represented by the solid line curve 73 and the flux pattern which is normal to the longitudinal axis 11' is represented by the dotted line curve 83. As can be seen, from a consideration of the solid line curve 73, the magnetic flux which is substantially parallel to the longitudinal axis 11' has a substantially constant magnitude in the upper and lower regions of core 11 falling to a zero flux field at the ends of the core and at the intermediate section of the core. The flux pattern which is normal to the longitudinal axis can be seen to be maximum at the intermediate region of core 11 as well as at the end regions thereof.

Considering the efiect of the fiux patterns shown in FIGURE 2, upon the armature 14, when the current signal I is impressed upon either of the coils to the exclusion of the other, it can be seen from the normal fiux patterns 81 and 82 shown in FIGURES 2(a) and 2(b) that the field strength in the immediate region of the air-gap 16 is zero so that no attractive forces will be brought to bear upon armature 14. However, in the case where a current signal I is applied to both of the pairs of windings simultaneously, a flux pattern which is normal to the core longitudin-al axis 11' is maximum in the intermediate region of core 11 so as to exert an attractive force upon armature 14 which overcomes the biasing force of spring 15 to urge armature 14 in the direction shown by arrow 22, thus moving the armature 14 into the latched state.

Removal of the current signal I does not remove the normal flux pattern 83, shown in FIGURE 2(c) due to the retentiv-ity characteristics of the semi-hard ferromag' netic core 11. Thus, even in the absence of any electrical power the armature 14 will be retained in the latched state.

The armature 14 may be released simply by application of'a current signal I having the direction shown in FIG- UR'E 1, with the current signal I preferably being with equal magnitude and reverse direction of the current signalII. This may be done simply by application of the original current signal I to the reversed terminals of the windings q-b and c-d thus avoiding the need for a separate current signal source. The application of a current signal I having the current direction shown in FIGURE 1 to both pairs of terminals a-b and c-d will set up a flux pattern shown by the phantom line curve 84 of FIGURE 2(c) 'which will substantially exactly counter the flux pattern 83 as to reduce the flux normal to the core longitudinal axis 11'- to substantially zero field strength in the intermediate region of core 11. The recurrence of a normal flux pattern of zero field strength in the intermediate region of core 11 will again place armature 14 under control of the mechanical biasing means or spring 15 causing it to be moved against the back stop 19 maintaining the armature 14 at a spaced distance from core 11 equal to the air-gap distance 16. Removal of the reverse current signal I from the input terminals a-b and c-d will not affect the resultant flux pattern remaining within the core 11 and the armature 14 will be retained in the released state under the control of spring means 15 in readiness for the next operation to move the device into the latched state which will occur in the same manner as was previously described.

It can clearly be seen from the foregoing description that the instant invention provides a novel electromagnet control device which may be operated to either its released or latched state and be retained in either of the two states indefinitely and in the absence of any electrical signal. The signal once applied may be removed without affecting in any way the state in which the device 10 will be maintained. If desired, a single current signal may be employed across the input terminals a and b simply by connecting the terminals c and b through a conductor 24 so as to apply the appropriate latching or releasing current to the pair of coils. The magnitude of the latching or releasing current applied is in no way critical so long as it reaches a magnitude at least suflicient to set up a normal flux pattern capable of developing an attractive force upon armature 14 which is sufiicient to overcome the biasing force of the mechanical spring means 15. It should also be understood that even in the case of equiping a yoke into the core the coils divided into two in the longitudinal direction of the core may be controlled in such a way that they may be connected in series for either latching or releasing without departing from the basic principles of the instant invention.

Although there has been described a preferred embodiment of this novel invention, many variations and modifications will now be apparent to those skilled in the art. Therefore, this invention is to be limited, not by the specific disclosure herein, but only by the appending claims.

What is claimed is:

1. An electromagnet control assembly comprised of a ferromagnetic core;

first and second coils inductively associated with said core;

said first c-oil being comprised of a first plurality of windings surrounding a first region of said core and a second plurality of windings surrounding a second region of said core;

said first and second windings being spaced a predetermined distance from one another;

said second coil having a third plurality of windings wound about said first region and a fourth plurality of windings wound about said second core region, said plurality of first and second windings being connected in series;

said plurality of third and fourth windings being connected in series;

an armature member being pivotally mounted at one 50 end thereof and having the opposite end thereof positioned adjacent the region of said core intermediate said first and second regions;

biasing means coupled to the free end of said armature for urging said armature generally away from said core; said first and second coils being adapted to receive cur- 5 rent signals for generating a magnetic flux pattern normal to the longitudinal axis of said core for attracting said armature member; said core member being of a ferromagnetic material having a retentivity characteristic to maintain the attractive force upon said armature even after the current signals have been removed.

2. The assembly of claim 1 further comprising stop means to prevent the free end of said armature from moving beyond a predetermined distance from said core to maintain a predetermined air-gap distance when said assembly is in the released state.

3. The assembly of claim 1 wherein said first and secand pluralities of windings are Wound in the same direction about said core.

4. The assembly of claim 1 wherein said third and fourth pluralities of windings are wound in the same direction about said core.

5. The assembly of claim 1 wherein said first and second pluralities of windings are wound in a first direction about said core;

said third and fourth pluralities of windings being wound in the reverse direction about said core.

6. The assembly of claim 1 wherein said first and second pluralities of windings are wound in a first direction about said core;

said third and fourth pluralities of windings being wound in the reverse direction about said core;

said first plurality of windings being twice the number of said second plurality of windings.

7. The assembly of claim 1 wherein said first and second pluralities of windings are wound in a first direction about said core; a

said third and fourth pluralities of windings being wound in the reverse direction about said core;

said first plurality of windings being twice the number of said second plurality of windings;

said fourth plurality of windings being twice the number of said third plurality of windings.

References Cited 

1. AN ELECTROMAGNET CONTROL ASSEMBLY COMPRISED OF A FERROMAGNETIC CORE; FIRST AND SECOND COILS INDUCTIVELY ASSOCIATED WITH SAID CORE; SAID FIRST COIL BEING COMPRISED OF A FIRST PLURALITY OF WINDINGS SURROUNDING A FIRST REGION OF SAID CORE AND A SECOND PLURALITY OF WINDINGS SURROUNDING A SECOND REGION OF SAID CORE; SAID FIRST AND SECOND WINDINGS BEING SPACED A PREDETERMINED DISTANCE FROM ONE ANOTHER; SAID SECOND COIL HAVING A THIRD PLURALITY OF WINDINGS WOUND ABOUT SAID FIRST REGION AND A FOURTH PLURALITY OF WINDINGS WOUND ABOUT SAID SECOND CORE REGION, SAID PLURALITY OF FIRST AND SECOND WINDINGS BEING CONNECTED IN SERIES; SAID PLURALITY OF THIRD AND FOURTH WINDINGS BEING CONNECTED IN SERIES; AN ARMATURE MEMBER BEING PIVOTALLY MOUNTED AT ONE END THEREOF AND HAVING THE OPPOSITE END THEREOF POSITIONED ADJACENT THE REGION OF SAID CORE INTERMEDIATE SAID FIRST AND SECOND REGIONS; BIASING MEANS COUPLED TO THE FREE END OF SAID ARMATURE FOR URGING SAID ARMATURE GENERALLY AWAY FROM SAID CORE; SAID FIRST AND SECOND COILS BEING ADAPTED TO RECEIVE CURRENT SIGNALS FOR GENERATING A MAGNETIC FLUX PATTERN NORMAL TO THE LONGITUDINAL AXIS OF SAID CORE FOR ATTRACTING SAID ARMATURE MEMBER; SAID CORE MEMBER BEING OF A FERROMAGNETIC MATERIAL HAVING A RETENTITIVY CHARACTERISTIC TO MAINTAIN THE ATTRACTIVE FORCE UPON SAID ARMATURE EVEN AFTER THE CURRENT SIGNALS HAVE BEEN REMOVED. 